1. Field of the Invention
The present invention relates to an electronic pedometer which is used by being mounted on a human body in order to electronically count the number of steps by a person having the electronic pedometer mounted thereon.
2. Description of the Prior Art
Heretofore, an electronic pedometer has been developed which is used by being mounted on a human body in order to count the number of steps by a user through an electronic processing.
In general, for counting of the number of steps, an acceleration caused by vertical movement of a user's body during walking is detected to count how many times the accelerations occur as the number of steps.
However, a problem arises in that various noises due to motions of daily life other than a walk are detected, and hence the number of steps cannot be precisely measured as has been pointed out formerly.
In order to solve this problem, there have been proposed a method in which as a filtering processing, after an acceleration is detected once, a predetermined dead zone time period is set to avoid misdetection due to noises (refer to Patent Document 1 for example), a method in which detection signals are counted as the number of steps only when it is detected that the detection signals are continuously outputted by the predetermined number of times (refer to Patent Document 2 and Patent Document 3 for example), a method in which a cycle of a walk is detected, and the number of steps is calculated from the cycle and a walk time period (refer to Patent Document 4 for example), and the like.
FIG. 3 is a block diagram of a pedometer described in Patent Document 1 described above. The pedometer includes: an acceleration detecting portion 301, which is used by being mounted on the body of a user, for detecting an acceleration caused by a walk of the user to output a signal (walk signal) corresponding to the walk; a filter portion 302 for outputting a signal having a predetermined cycle corresponding to a walk cycle from the output signal from the acceleration detecting portion 301; a walk cycle calculating portion 306 for calculating a walk cycle as a reference by averaging a predetermined number of signals of the signals outputted from the filter portion 302; a walk cycle comparing portion 303 for comparing a cycle of each signal outputted from the filter portion 302 with the walk cycle as the reference calculated in the walk cycle calculating portion 306 to output a signal having a cycle similar to the walk cycle as the above reference of the signals outputted from the filter portion 302; a step number counting portion 304 for counting signals from the walk cycle comparing portion 303; and a display portion 305 for displaying thereon a count value obtained through the counting in the step number counting portion 304. It should be noted that the filter portion 302, the walk cycle comparing portion 303, the step number counting portion 304, and the walk cycle calculating portion 306 can be configured with a central processing unit (CPU), and a storage portion for storing therein a program to be executed by the CPU.
The acceleration detecting portion 301 detects an acceleration caused by a walk of a walker to output a signal corresponding to the walk. The filter portion 302 outputs a signal having a predetermined cycle corresponding to a walk cycle from the output signal of the acceleration detecting portion 301. The walk cycle calculating portion 306 calculates a walk cycle as a reference by averaging a predetermined number of signals of the signals outputted from the filter portion 302. The walk cycle comparing portion 303 compares a cycle of each signal outputted from the filter portion 302 with the walk cycle as the reference calculated in the walk cycle calculating portion 306 to output a signal having a cycle similar to the walk cycle as the above reference of the signals outputted from the filter portion 302. The step number counting portion 304 counts signals from the walk cycle comparing portion 303 as signals corresponding to the walk. The display portion 305 displays thereon data on the number of steps as a count value obtained through the counting in the step number counting portion 304.
In such a manner, the electric pedometer is configured such that the walk cycle comparing portion 303 outputs the signals which are generated with a cycle similar to the walk cycle as the reference. Thus, a predetermined dead zone is provided so as not to detect any of the signals which are generated for time periods other than the time period similar to the time period having the walk cycle. As a result, it becomes possible to avoid that the noise is detected as the signal caused by the walk by mistake.
FIG. 4 is a signal waveform chart for explaining a signal detecting operation of the above conventional electronic pedometer, and shows an example of an electronic pedometer employing a system in which an acceleration sensor is mounted on an arm of a user in order to measure the number of steps by the user. In FIG. 4, an axis of abscissa represents time, and an axis of ordinate represents an acceleration detected by the acceleration detecting portion 301. Intersection positions (positions on a time base indicated by arrows) between the acceleration signal waveform and a reference level X represent a walk detected by the electronic pedometer. Since a cycle of the acceleration signal waveform is T, and the electronic pedometer employs the system in which the acceleration sensor is mounted on an arm of a user, two steps are detected per cycle T.
Actually, it is very difficult to detect only the acceleration caused by the vertical movement in a walk. The acceleration is influenced by operations other than a walk in daily life, and idle operations such as an operation of shaking arms in a walk. Thus, the detected acceleration signal is obtained as the sum of signals of those operations. For this reason, there is encountered a problem that a detection level fluctuates, and hence a walk signal which should be normally detected is not detected, but is omitted. That is, valley portions 401, 402 and 403 in FIG. 4 ought normally to drop below the reference level X to intersect the reference level X, whereby the intersection positions ought to be counted as the number of steps. However, there is encountered a problem that since the detection level fluctuates and omission is generated in the walk signal to be detected, the counting leakage occurs.
<Patent Document 1> JP 56-86309 A
<Patent Document 2> JP 63-262784 A
<Patent Document 3> JP 3,017,529 B
<Patent Document 4> JP 2,697,911 B
It is an object of the present invention to carry out measurement of number of steps more precisely even when a sufficient detection signal for a walk cannot be obtained.